Sonic and especially ultrasonic energy is increasingly utilized in the non-destructive inspection or testing of parts for defects. A typical form of such testing or inspection apparatus provides a quantity of liquid (e.g., water) on the part to be tested as a coupling means for sonic energy generated by a remotely located transducer. It has been found that even a very small amount of irregularities in the surface of the projected liquid column produces sonic reflections and refractions which result in loss of sonic energy through the walls of the projected liquid column to the test piece reducing operational efficiency.
U.S. Pat. No. 4,393,991, Sonic Water Jet Nozzle, by N. B. Jeffras and R. H. Torgersen includes an elongated generally tapering nozzle with a larger end of which a sonic transducer is located. A plurality of openings in surrounding relationship to a transducer that inhibits rotation of a liquid which encompasses the vibrating face of the transducer and which fills the internal nozzle parts in a continuously moving stream. Fin-like means are located at an intermediate location along the tapering passageway through the nozzle to further reduce the stream degradation caused by rotating or swirling. As a result of this patented construction, a highly uniform flow of liquid is provided along which pulsating sonic energy can be transmitted from the transducer to the surface of the test piece. A homogeneous or solid stream of liquid is produced with this patented device which is almost twice as long as that projected by prior known devices.
Although substantial improvement over known prior devices is achieved, the patented device requires that the sonic transducer and liquid column must be coaxial which may be inconvenient or impossible in certain use situations.